A Syrian victim who suffered an alleged chemical attack at Khan al-Assal village receives treatment by doctors at a hospital in Aleppo, Syria, on Tuesday. / SANA via AP

by Janelle Dumalaon and Jacob Russell,
Special for USA TODAY

by Janelle Dumalaon and Jacob Russell,
Special for USA TODAY

ARBAT, Iraq - Whether Syria crossed a "red line" by using chemical weapons in its battle against a rebellion appeared murky Wednesday and both sides in the war blamed the other for an attack that Western nations are unsure even happened.

The Syrian regime of Bashar Assad blamed rebels for an attack Tuesday in the village of Khan al-Assal that killed at least two dozen people, according to anti-Assad groups. Syria asked the United Nations to investigate.

The United Nations announced Thursday that it will investigate the possible use of chemical weapons in Syria, which would amount to a crime against humanity, Secretary-General Ban Ki-moon said.

Syria's main opposition group, the Syrian National Coalition, also demanded an international investigation into claims that could not be independently verified because the area is largely sealed off from journalists.

"All evidence now indicates that the Assad regime is using these weapons against its own people," the Western-backed opposition group stated.

The United States says Assad has a massive store of chemical weapons, but experts say the regime probably would not use them, and opposition forces could not use them.

"All we really have to go on are the claims of the regime and the opposition, neither of which are very credible," said David Hartwell, Middle East analyst at IHS Jane's in London. "If you were looking at an attack with chemical munitions, you would expect an awful lot more casualties than the deaths yesterday." IHS Jane's is an intelligence and security company.

The event could be critical, because President Obama has said the use of chemical weapons by the regime would be a "red line" offense that would cause him to rethink his position of not using military forces to stop Assad, whose forces have killed 80,000 people with conventional weapons in the two-year conflict, according to the United Nations.

Obama, in Israel for a diplomatic mission, said that the United States is investigating the allegations but that he is "deeply skeptical" of claims by Assad, whom he has said needs to be removed from power.

The Syrian official news agency SANA on Wednesday published pictures of wounded people in a hospital ward, allegedly victims of a rebel chemical attack.

Syria's U.N. Ambassador Bashar Ja'afari called the attack "very serious and alarming and unacceptable and unethical." He said Syria asked the secretary-general of the U.N. for assistance "in a sign of good faith, good will, good intentions" to the international community, international public opinion and the Syrian people.

Even so, Hartwell questioned the regime's preparedness, as well as the opposition's capacity, to bring chemical weapons into the mix of fighting as the uprising enters its third year.

"I find it unlikely that the Syrian regimewould have taken this step (using chemical weapons), knowing the consequences that it would invite" he said. "Similarly, I also doubt that the opposition would either have the ability or the munitions to do that."

There are multiple scenarios as to what could have taken place Tuesday that analysts said were at least as plausible as chemical weapons. The Syrian military may have fired a Scud missile into Aleppo, and the resulting chlorine odor given off by the missile's fuel components led people to believe that chemical weapons had been used. Or a missile may have been fired into an agricultural facility and released the same odor.

Israel seemed convinced something had occurred. Yuval Steinitz, minister of intelligence and strategic affairs, said it is "apparently clear" that chemical weapons were used. A Reuters photographer said victims he had visited in Aleppo hospitals were suffering breathing problems.

While it's unlikely that Assad or anyone else used chemical weapons such as nerve or mustard gas, videos of the attack and victims appear to show some kind of chemical agent was used, said Tony Badran, a Syria analyst at Foundation for Defense of Democracies in Washington.

"It could be an improvised chemical attack like chlorine or something toxic like pesticides," Badran said. "Whatever it is, we don't have any evidence yet that clearly shows this was anything that could be blamed on the rebels."

Opposition activists said that if investigations reveal that Assad had indeed used chemical weapons, it should force the West to drop its posture of non-intervention in the conflict.

"Barack Obama and the European heads of state have said they will not stand for that," said Hozan Ibrahim, a Syrian activist based in Berlin.

Robert Ford, U.S. ambassador to Syria, told the House Foreign Affairs Committee on Wednesday that there was "no evidence to substantiate the reports that chemical weapons were used yesterday," but stressed that investigations were ongoing to shed light on the matter.

Hartwell says that opposition activists have little reason to hope that the incident should pave the way for Western military intervention.

"I think there are all sorts of caveats to that promise", he said. "I think if it were a small-scale attack with a small number of casualties, the West would find excuses not to get involved. But if it were a large attack on an urban area, or critical intelligence existed saying that Syria's chemical weapons were moving, then that makes a better case for intervention."